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which, along with the auxiliary pumping action of the contracting skeletal muscles, greatly increases venous return. The increases in heart rate and myocardial contractility, both induced by the activation of cardiac sympathetic nerves, enables the heart to transfer blood to the pulmonary and systemic circulations, thereby increasing cardiac output. Stroke volume increases only slightly. O2 consumption and blood O2 extraction increase, and systolic pressure and mean blood pressure increase slightly. As body temperature rises during exercise, the skin blood vessels dilate. However, when the heart rate becomes maximal during severe exercise, the skin vessels constrict. This increases the effective blood volume but causes greater increases in body temperature and a feeling of exhaustion. The limiting factor in exercise performance is delivery of blood to the active muscles.
6. Acute blood loss induces tachycardia, hypotension, generalized arteriolar constriction, and generalized venoconstriction. Acute blood loss invokes a number of negative feedback (compensatory) mechanisms, such as baroreceptor and chemoreceptor reflexes, responses to moderate cerebral ischemia, reabsorption of tissue fluids, release of endogenous vasoconstrictors, and renal conservation of water and electrolytes. Acute blood loss also invokes a number of positive feedback (decompensatory) mechanisms, such as cardiac failure, acidosis, central nervous system depression, aberrations in blood coagulation, and depression of the mononuclear phagocytic system. The outcome of acute blood loss depends on the sum of gains of the positive and negative feedback mechanisms and on the interactions between these mechanisms.
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SECTION 5The Respiratory System MICHELLE M. CLOUTIER AND ROGER S. THRALL
Upon completion of this chapter, the student should be able to answer the following questions: 1.
Explain the anatomical structure/function relationships of the upper and lower components of the respiratory system.
2.
Compare and contrast the pulmonary and bronchial circulatory systems.
3.
Explain the relationships between innervation and muscles in the control of respiration.
4.
Compare and contrast the roles of the conducting airways and components of the respiratory unit.
5.
Compare and contrast the effects of stimulation of the parasympathetic and sympathetic nervous systems on respiratory responses.
6 Describe lung development and alveolar repair after injury to regeneration of normal architecture.